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| United States Patent |
6,228,273
|
|
Hammonds
|
May 8, 2001
|
Apparatus and method for control of rate of dissolution of solid chemical
material into solution
Abstract
An apparatus and method for dissolving various forms of chemicals in solid
material form into a liquid solution is disclosed. The apparatus includes
a fluid reservoir to which an ultrasonic generating device is attached,
capable of creating an acoustic wave that induces alternating compression
and rarefaction fronts that react with microscopic inclusions in the
liquid to produce cavitation. The cavitation phenomenon works on
microscopic inclusions or bubbles or entrained air and or vapor of the
liquid. The release of energy during this process causes solids held
together by binders to become separated and be blended into solution at a
consistent and predictable rate. The chemical to be supplied may be in
solid form either in a pelletized or granular form arranged in a vertical
column with only the lower portion of the column submerged in the solution
with the level of submersion being adjustable. As fluid is circulated
through the reservoir, chemical is introduced to the solution providing
consistent dissolution of chemical. Solution strength is determined by a
combination of flow rate through the reservoir, intensity and/or frequency
of the ultrasonic action and the submersion level of the solid chemical
material. Solution is delivered to various processes through either
gravity flow as it exits the reservoir or a pump capable of delivering the
solution into a pressurized line or vessel.
| Inventors:
|
Hammonds; Carl L. (Humble, TX)
|
| Assignee:
|
Hammonds Technical Services, Inc. (Houston, TX)
|
| Appl. No.:
|
376547 |
| Filed:
|
August 18, 1999 |
| Current U.S. Class: |
210/748; 210/205; 422/128 |
| Intern'l Class: |
C02F 001/48 |
| Field of Search: |
422/128
210/748,205
|
References Cited
U.S. Patent Documents
| 2717874 | Sep., 1955 | Verain.
| |
| 3582285 | Jun., 1971 | Hamilton.
| |
| 3956132 | May., 1976 | Takemitsu.
| |
| 4720374 | Jan., 1988 | Ramachandran | 422/310.
|
| 4749537 | Jun., 1988 | Gautschi et al. | 264/232.
|
| 4961860 | Oct., 1990 | Masri.
| |
| 5124050 | Jun., 1992 | Ushimaru et al.
| |
| 5218983 | Jun., 1993 | King | 137/1.
|
| 5395592 | Mar., 1995 | Bolleman et al.
| |
| 5976385 | Nov., 1999 | King | 210/754.
|
| 6090295 | Jul., 2000 | Raghavarao et al.
| |
Primary Examiner: Barry; Chester T.
Attorney, Agent or Firm: Bush; Gary L.
Mayor, Day, Caldwell & Keeton, LLP
Parent Case Text
REFERENCE TO PRIOR APPLICATION
This application claims priority from Provisional Application 60/097,705
filed Aug. 21, 1998.
Claims
What is claimed is:
1. Apparatus for controlling the dissolution rate of solid chemical
material, comprising
a fresh water tank,
a fluid holding tank having a fluid inlet fluidly connected to said fresh
water tank and a fluid outlet line and an interior space for holding
fluid, said fluid holding tank arranged and designed such that fresh water
enters from said fresh water tank via said fluid inlet and treated water
exits via said outlet line,
a perforated chemical material feeder disposed in said tank, said feeder
designed and arranged to hold said chemical material in an essentially
vertical orientation, with said fluid in said tank entering and exiting
perforations of said feeder to wet and dissolve at least a portion of said
solid chemical material in said feeder,
an ultrasonic generator having a probe coupled with said tank which applies
ultrasonic waves to the interior of said tank for producing a cavitation
intensity of said liquid in said tank and in said feeder, whereby said
cavitation erodes said chemical material for dissolving in said liquid,
and
means for varying a characteristic of said ultrasonic waves in order to
vary the rate of dissolution of said chemical material in said liquid.
2. The apparatus of claim 1 wherein,
said characteristic of said ultrasonic waves is the intensity of the waves.
3. The apparatus of claim 1 wherein,
said characteristic of said ultrasonic waves is the frequency of the waves.
4. The apparatus of claim 1 wherein,
said perforated feeder is adapted to hold chemical material in the form of
tablets.
5. The apparatus of claim 1 wherein,
said perforated feeder is adapted to hold chemical material in the form of
granular material.
6. The apparatus of claim 1 wherein,
said chemical material includes calcium hypochlorite and said fluid is
water.
7. The apparatus of claim 1 further comprising,
a pump in said fluid outlet line, whereby,
said pump in said outlet line establishes a flow rate of liquid through
said tank.
8. A method for controlling the dissolution rate of solid chemical material
placed in a perforated feeder disposed in a liquid holding tank which has
a liquid inlet line and a liquid outlet line where the feeder is designed
and arranged to hold said chemical material in a vertical orientation,
with said liquid in said tank entering and exiting perforations of said
feeder to wet and dissolve at least a portion of said solid chemical
material in said feeder, the method comprising the steps of,
producing a cavitation intensity of said liquid in said tank by means of
ultrasonic waves to the interior of said tank, whereby said cavitation
enters said perforated feeder and erodes said chemical material in said
perforated feeder for dissolving in said liquid, and
varying a characteristic of said ultrasonic waves in order to vary the rate
of dissolution of said chemical material in said liquid.
9. The method of claim 8 wherein,
said characteristic of said ultrasonic waves is the intensity of the waves.
10. The method of claim 8 wherein,
said characteristic of said ultrasonic waves is the frequency of the waves.
11. The method of claim 8 further comprising the steps of,
establishing a flow rate of liquid through said tanks and through said
perforated feeder, whereby a level of chemical dissolution of said
chemical material in said liquid of said liquid output line is a function
of said flow rate of liquid through said tank and said cavitation
intensity of liquid in said tank.
12. Apparatus for controlling the dissolution rate of solid chemical
material comprising,
a source of fresh water,
a liquid holding tank having a fluid inlet and a fluid outlet line and an
interior space for holding liquid, said fluid inlet fluidly connected to
said source of fresh water,
a perforated chemical material feeder disposed in said tank, said feeder
designed and arranged to hold said chemical material in an essentially
vertical orientation, with said liquid in said tank entering perforations
of said feeder to wet and dissolve at least a portion of said solid
chemical material in said feeder, and
an ultrasonic generator having a probe coupled with said tank which applies
ultrasonic waves to the interior of said tank for producing a cavitation
intensity of said liquid in said tank and in said feeder, whereby said
cavitation erodes said chemical material for dissolving in said liquid to
produce treated liquid in said tank, said fluid outlet line being arranged
and designed to transfer treated liquid from said tank.
13. The apparatus of claim 12 wherein,
said ultrasonic generator includes a mechanism which varies a
characteristic of said ultrasonic waves in order to vary the rate of
dissolution of said solid chemical material.
14. The apparatus of claim 13 wherein,
said characteristic of said ultrasonic waves is the intensity of the waves.
15. The apparatus of claim 13 wherein,
said characteristic of said ultrasonic waves is the frequency of the waves.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates generally to the field of controlling the rate of
dissolution of solid chemical material, such as in tablets, granules,
etc., into liquid solution. In particular the invention relates to
controlling the rate of dissolving calcium hypochlorite tablets or "pucks"
in water for making the water safe for drinking by human beings.
2. Description of the Prior Art
Water used for human consumption, food processing, industrial cooling,
washing, swimming and lubrication requires various levels of disinfection
in order to prevent growth of various bacteria and fungi that threaten
human health as well as damage industrial equipment and processes. Calcium
hypochlorite is but one of several popular chemicals used for
disinfection. However, calcium hypochlorite must be introduced in a
controlled manner which will ultimately produce residuals in water in the
range of 0.1-5 PPM (parts per million).
Erosion has been the primary means of dissolving solid chemical tablets or
granules in the past. Submitting chemical tablets, pellets, solid
cylindrical sticks or granules to a controlled flow rate of water has been
used to dissolve the solid. Varying the flow rate, which in effect changes
the rate of erosion of the solid chemical material through surface
friction of liquid abrading against the solid, has been the primary means
of control. A higher flow rate dissolves more chemical material into the
water, and vice versa.
Varying of the flow rate accomplishes one of two goals. It either increases
velocity of the water against the same amount of solid chemical material,
or raises the liquid level in the reservoir which increases the amount of
wetted surface of the solid chemical material. A combination of a more
intense erosive action or greater wetted surface area of the chemical
material theoretically changes the concentration of the solution being
created by the process.
Current erosion feeder technologies all share common shortcomings. Since
the various shapes of solids are typically stacked either in an orderly
form or applied randomly within a container, their surface geometry varies
relative to the direction of flow of the dissolving fluid. Some surfaces
are perpendicular to the flow and some are at various angles; therefore
the erosive effect of the fluid against the solid varies throughout a
given load of tablets. Since solid tablets are typically arranged in a
vertical column above the wetted area, and are fed through gravity weight
of the tablets as dissolution takes place, the dissolution rate also
varies with any given flow rate of fluid across the exposed tablets. As
the dissolution varies, so does the strength of the resulting solution
exiting the system.
Erosion feeders break down solid chemical tablet structure largely through
the action of water molecules physically abrading the solid chemical
material (e.g. tablet), causing it to be dissolved. The erosion action of
the water on the tablets of the feeder varies with changes in velocity and
resulting intensity of the eroding fluid striking the tablet. Therefore,
subtle differences in the shape and attitude of the chemical solid
material in relation to the direction of flow of fluid affects the rate
and consistency of erosion. Erosion rates are further influenced by
increasing or decreasing the amount of solid chemical material being
exposed to the eroding flow of fluid. This occurs when the fluid level
within the feeder is changed or when the fluid flow rate within the feeder
is changed.
Controlling the flow rate of the dissolving fluid across the wetted area of
the solid chemical material requires various controls, valves and fluid
flow measuring equipment. Since system supply pressure of such dissolving
fluid can and often does vary, maintaining a consistent erosion rate and
subsequent solution strength is extremely difficult, often requiring a
complex system of controls. If automatic controls are called for, the
mechanical actuation of such controls is often complex and costly.
"Turn-down", or the ability to vary the amount of chemical into liquid of
the feeder, is extremely important. Since erosion rates of various solid
chemical materials (of tablets or granules) depends largely on a physical
action point, the rate of erosion often becomes unpredictable in the lower
ranges. Current technology erosion feeders do not typically produce a
linear response to changes in flow rates. As a result, when systems are
"turned-down" from very high chemical dissolution levels to very low
levels, consistency and accuracy is sacrificed. Therefore, large systems
are not generally capable of delivering very small chemical dissolution
levels, and smaller systems have upper limits due to volumetric capacity
of both solid chemical and eroding fluid.
Erosion feeders depend on relatively large volumes of liquid to effect the
erosion process. Therefore, applications requiring small amounts of
dissolved chemical at a very precise rate are not generally applicable.
Fluid handling equipment such as pumps and piping must be sized to handle
large volumes of liquid, and since the control of the system is
accomplished through varying the flow rate through the chemical deliverer
(e.g., chlorinator), the equipment used to deliver the final solution must
also be controllable, making the choice and arrangement of these various
flow controlling devices critical to feeder performance.
Erosion is further complicated because the process of producing various
chemicals in solid form depends on the application of chemical binders and
hydraulic compaction. Even subtle variations in the manufacturing process
causes inconsistencies in dissolution rates, because the solids often have
soft or hard areas within the solid form. This factor makes water velocity
and angle of incidence even more critical in the erosion process.
Since many water disinfection applications require extremely small amounts
of chemical residual to be placed into solution, current technology does
not provide consistent performance due to excessive flow rates required to
effect dissolution. The inconsistent performance has been due to
difficulties in controlling the flow volume and complexity of the system.
As a result prior technologies have not been cost-effective. Installations
such as very low volume water wells and chemical processes require only
minute quantities of chemical in very small amounts of treating solution.
Current technology cannot provide these levels of delivery and consistency
since residual chemical must be delivered in as little as 0.5 parts per
million.
IDENTIFICATION OF OBJECTS OF THE INVENTION
A principal object of the invention is to provide a method and apparatus
for controlling the rate of a solid chemical dissolution into a liquid
which does not rely on varying the flow rate of the liquid across the
solid chemical material.
Another important object of the invention is to provide a water
chlorination system which is capable of dissolving small quantities of
chlorine at consistent levels (parts per million) in small amounts of
water.
SUMMARY OF THE INVENTION
The invention relates to the dissolution of any solid chemical material
into any liquid in order to control the rate of chemical dissolved in that
liquid. The preferred embodiment of the invention is to dissolve a solid
source of chlorine, e.g., calcium hypochlorite tablets or "pucks", into
water for chlorinating the water in order to make it safe for drinking,
washing, and the like. Fresh water enters a tank which has a perforated
cylinder filled with solid chlorine-source tablets or granules such as
calcium hypochlorite. A source of ultrasonic energy produces cavitation of
the water in the tank. The cavitating water erodes the calcium
hypochlorite puck or granules. The higher the level of ultrasonic energy
applied, the higher the cavitation of the water in the tank, and the
higher the resulting rate of erosion and dissolution of the solid chemical
material into the water. Thus, the rate of dissolution of chemical, e.g.
chlorine into water, is controlled by varying the intensity of ultrasonic
waves in the water from an ultrasonic generator.
BRIEF DESCRIPTION OF THE DRAWINGS
The objects, advantages, and features of the invention will become more
apparent by reference to the drawings which are appended hereto and
wherein like numerals indicate like parts and wherein an illustrative
embodiment of the invention is shown, of which:
FIG. 1 is a schematic illustration of the apparatus of the invention
showing the application of controlled ultrasonic energy to a water tank
thereby producing cavitation in a tank for the erosion of solid chemical
material into a liquid;
FIG. 2 is a graphical illustration of the rate of dissolution of solid
chemical material into liquid as a function of intensity of ultrasonic
energy applied; and
FIG. 3 is a graphical illustration of the rate of dissolution of solid
chemical material into liquid as a function of frequency of ultrasonic
energy applied.
DESCRIPTION OF THE PREFERRED EMBODIMENT OF THE INVENTION
FIG. 1 shows the apparatus of this invention which includes a water tank 10
arranged and designed for the dissolving of chlorine from solid chemical
material, such as tablets or pucks 15 or granules of calcium hypochlorite.
The preferred embodiment of chlorinating water is but a species of the
generic invention of dissolving chemical into any liquid from any solid
chemical source. FIG. 1 shows that a tank 5 receives a source of fresh
water prior to its final chlorination stage to make the water suitable for
human use, such as drinking, bathing, etc. A line 8 feeds water to a
chlorination tank 10 which includes a chlorination tablet column 20 filled
with granules or tablets (pucks) of calcium hypochlorite. Perforations 12
in the column allow the water in the tank 10 to fill the column 20 at
substantially the same level as that of tank 10. Typically, the column 20
is filled with tablets 15 or granules to a level which extends above the
level of water in the tank 10 so that as the tablets erode, more tablets
are lowered by gravity and sink into the liquid of the tank, thereby
continuing the dissolution process.
An ultrasonic generator 50, controlled by a power source 55, applies
ultrasonic waves 57 via inlet 52 in order to produce cavitation of the
liquid in tank 10. The cavitating water, via the perforations 12 in the
column, act on the tablets 15 to dissolve or erode them. The intensity of
cavitation can be controlled in one or both of two modes. The first is to
change the intensity of the ultrasonic waves by varying the input to the
ultrasonic generator 50, e.g., by power source 55. The second is to change
the frequency of the ultrasonic waves by varying the ultrasonic controls
50.
FIG. 2 shows that the rate of chemical dissolution increases with increases
in the intensity of the ultrasonic waves applied to tank 10, and FIG. 3
shows that the rate of chemical dissolution increases with the frequency
of ultrasonic waves. A combination of intensity and frequency control can
be arranged and designed to precisely control the rate of chemical
dissolution for any solid chemical source material and liquid, but
specifically for calcium hypochlorite and water.
A pump 22 connected to a line 18 from tank 10 produces an output stream of
water at substantially constant flow rate. As a result, the flow rate in
line 8 which inputs water into tank 10 is at a substantially constant flow
rate, and the level of water in the tank 10 is at a substantially constant
level. Nevertheless the level of liquid in tank 10 may be varied thereby
further controlling the rate of dissolution of chemical into the liquid in
the tank.
The controlled use of ultrasonic waves into the water of tank 10 changes
the erosion process of tablets 15. Erosion is effected through the use of
cavitation within the fluid, causing the formation of microscopic bubble
inclusions that work against the dry solid chemical material in all
directions without consideration to the velocity of liquid flow moving
through the process. Further, erosion is precisely controlled by
increasing or decreasing the intensity or frequency (or both) of
cavitation within a given volume of water. Since the process works equally
well in large or small volumes of fluid, neither the volume of water nor
the flow rate of water moving across the chemical tablets is critical. The
intensity of ultrasonic cavitation is matched with whatever volume of
fluid is present in order to effect the desired degree of dissolution.
Control of the process is reduced to a simple electrical control that
varies the intensity of the ultrasonic modulation within the fluid. Flow
rates of fluid can remain constant, but of course can be varied if
desired.
Since the excitation of inclusions or microscopic bubbles with a fluid
through cavitation is capable of producing very aggressive dislodging of
solids, the process lends itself to the breakdown of solid materials being
placed into solution through dissolution.
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